Ka'b bin 'Ujra reported that he entered the mosque and saw Abdul Rahman bin Umm Hakam delivering the sermon in a sitting posture. Upon this he said: Look at this wretched person; he delivers the sermon while sitting, whereas Allah said:" And when they see merchandise or sport, they break away to it and leave thee standing."
Explanation & Benefits
Shaykh Maulana Abdul Aziz Alvi
Hadith Commentary: Benefits and Issues:
From this hadith, it is understood that the noble Companions (radi Allahu anhum ajma'in) would not tolerate any act contrary to the Sunnah; they would immediately admonish the one committing such an act.
Therefore, when Ka'b bin Ujrah (radi Allahu anhu) saw Abdur Rahman bin Umm al-Hakam delivering the sermon while sitting, he openly said:
Look at this wicked one,
that is, he called him by the name "wicked."
Source: Tuhfat al-Muslim: Commentary on Sahih Muslim, Page: 2001